The present invention. More particularly, the invention relates to a multi-mode amplifier having at least one rhythm mode channel and at least one dissimilar, and alternately selectable, distortion mode channel, each channel devoted to producing the performance of an individual mode.
Amplifiers for electric guitar offering two or more different modes of operation are well known and in use. Typically the two modes comprise one mode of substantially linear operation for undistorted xe2x80x9cRhythmxe2x80x9d playing while the other mode offers distortion enhancement for xe2x80x9cLeadxe2x80x9d performance. Examples cited include the original xe2x80x9cDual Modexe2x80x9d patent of the present inventor: U.S. Pat. No. 4,211,893, which, having undergone several evolutionary improvements, remains at the time of this filing, a leading commercial product.
Other examples of dual mode architecture may also be cited including U.S. Pat. No. 4,701,957 (Smith) which teaches a simplified dual mode design, and in U.S. Pat. No. 5,012,199 (McKale), teaching a dual-mode design in which all tube stages remain active in all modes.
An important common denominator of all dual mode prior art is the use of a single signal path of amplifier stages arranged in a series fashion, one stage after the other. And although these units are commonly called xe2x80x9cdual channelxe2x80x9d or xe2x80x9cchannel switchingxe2x80x9d, they are actually xe2x80x9csingle channel, dual MODExe2x80x9d. This is important because the distinction between modes and channels is central to the present invention.
For clarity, a xe2x80x9cchannelxe2x80x9d is correctly defined as a signal path, whereas a xe2x80x9cmodexe2x80x9d is an operating or performance characteristic. A given mode of performance would be the result of a signal having been processed by passing through a channel of amplification.
Before the advent of the distortion generating lead mode of the ""893 amplifier, there was only one mode: clean rhythm. And even though dual channel amplifiers were well known and easily predate the ""893 unit, both channels of such amplifiers were substantially alike: each had its own separate input terminal and each one provided only clean rhythm mode performance. The purpose was so that two guitars, or one guitar and a vocal microphone could be accommodated simultaneously by the one amplifier. Thus, examples of dual channel, single mode amplifiers are common.
The ""893 amplifier was the first example of a dual mode amplifier, and the two modesxe2x80x94rhythm and leadxe2x80x94were selected alternately and both were produced within a single channel, series configured chain of amplifier stages. It is not an exaggeration to say that the introduction of the distortion mode of performance has left a permanent imprint on popular music because, when properly rendered, the lead distortion sound provides a new voice and an effective new realm of musical expression to the guitarist. The varying performance characteristics of the modes in the ""893 amplifier and its stylistic followers are achieved by altering the gain structure of what is invariably a single channel signal path of gain stages arranged one after the other. By the addition of extra gain stages, and/or the altering of gain within the individual stages plus the interstage components, different performance modes are achieved. These amplifiers would be described as having dual or multi-performance modes all within a single channel.
As the ""893 product evolved and finally arrived at its full, no-comprise performance stature, it required well over two dozen switching devices to enable the single channel circuit to deliver uncompromised multi-mode performance, including separate user controls dedicated to each. Thus, this created a strong need to develop an amplifier configuration that simplified the switching requirements, yet offered performance on a par with that of the fully embellished ""893 product.
Simultaneous with the need for simplified switching requirements, there arose the need for an amplifier which could provide resolution to the dilemma of tone control location. Locating the tone controls near the input of the signal path yields superior rhythm mode performance because the signal amplitude is reduced and shaped to the appropriate EQ curve early on, thereby limiting unwanted overload of subsequent gain stages. Unfortunately, tone controls in this position are not so effective for heavy distortion performance because, as the signal undergoes further amplification in the massively, saturated distortion stages, it is the response curves inherent in these later stages which largely characterize the sound. At high settings of gain, saturation distortion occurs over the entire frequency range; thus frequencies boosted by the tone controls and present at the input to the distortion stages emerge from its output with less emphasis. The effect is somewhat like squeezing a pre-shaped form through an extrusion die: wherever the preshape exceeds the boundaries of the extrusion die, the part emerges resembling the extrusion die, not the input shape.
On the other hand, amplifiers with tone controls located at the end of the signal chain (or at least after the saturation stage(s), such as disclosed in U.S. Pat. Appl. Ser. No. 07/823,329, provide strong tone control action because subsequent stages operate substantially linearly and the effect described above is avoided. But achieving pristine clean sounds with these amplifiers can be difficult because a signal not attenuated and shaped early on is likely to cause unwanted saturation distortion before arriving at the tone controls.
Achieving maximum sonic performance in a multi-mode amplifier may further require a switch means to alter the operating voltages in accordance with mode selection such that differing power supply characteristics, which are individually optimized for each mode, are applied to the circuit in accordance with mode and/or channel selection.
The present invention substantially overcomes the limitations of the prior art by providing a parallel channel, multi-mode pre-amplifier which has at least two discrete amplifying channels, with at least one channel for a rhythm mode and at least another channel for a distortion mode including at least one distortion producing amplifier.
More specifically, the present invention provides a parallel channel, multi-mode pre-amplifier design, where each of the alternately selectable, parallel channels is devoted to producing the performance of an individual mode, i.e. rhythm or lead (distortion) mode. The present invention simplifies the complexity of the switching means required to provide improved performance in each stage of the design so that a tone control network may be optimally located within each channel for best performance the channel""s mode. The tone control network for the rhythm channel(s) can thus be located near the input of the pre-amp, while the tone control for the lead channel(s) can be located after the distortion stage(s) which would generally be nearer to the output of the preamp. Further, a switchable low impedance/buffer stage may optionally be used to drive the tone control network which allows for different user-selectable dynamic responses.
In one embodiment, the present invention also provides a multi-mode, parallel channel amplifier which has a single set of programmable, user adjustment controls, thereby obviating the need for a further set of controls. In another embodiment of the present invention, two sets of independent, user adjustment controls are provided, each dedicated to a particular channel/mode. In the latter embodiment, the necessity for a switch means within the amplifying circuit is reduced in comparison to a single channel series amplifier of equivalent performance capabilities.
The present inventin also provides for an improved outboard effects interface system which, in one embodiment, includes a single master control per channel combined with an effect send level control, while the output level control doubles as an effect return level control.
The present invention further provides a power supply switch means which allows a parallel channel amplifier, having at least two modes, to switch between at least two different power supply configruarions so lthat each channel may receive power by an optimized power source.
It is therefore one object of the present invention to provide a multi-mode amplifier which reduces the complixity of the switching means required to provide improved performance in at least two modes.
It is another object of the present invention to provide a multi-channel amplifier kwhich has at least two alternately selectable, paralles channels, each of which is devoted to producing performance of an individual mode.
It is a further object of the present invention to reduce the complexity of the switching means required for an alternately selectable, parallel channel amplifier while not compromising the performance of each of the stages in the design.
It is a further object of the present invention to provide an alternately selectable, parallel channel amplifier which has a tone control network optimally located within each channel for the best performance of each channel""s mode.
It is a still further object of the present invention to provide a switchable low impedance/buffer stage which may be used to drive the tone control network.
It is a still further object of the present invention to provide an improved outboard effect interface system which includes a one mastere control per channel, an effect mix control and an output level control.
It is also an object of the present invention to provide a power supply switch means which allows a paralles channel amplifier, having at least two modes, to switch between at least two different power supply configurations so that each channel may be powered by a optimized power source.
These and other objects of the invention will be better understood from the following Detailed Description of the Inventions, taken together with the attached Figures.